Minimally invasive medical techniques are aimed at reducing the amount of extraneous tissue that is damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. The average length of a hospital stay for a standard surgery may also be shortened significantly using minimally invasive surgical techniques. Thus, an increased adoption of minimally invasive techniques could save millions of hospital days, and millions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects, and time away from work may also be reduced with minimally invasive surgery.
The most common form of minimally invasive surgery may be endoscopy. The endoscopic surgical instruments generally include an endoscope (for viewing the surgical field) and working tools. In endoscopic surgery, the working tools are similar to those used in conventional (open) surgery, except that the working end or end effector of each tool is separated from its handle by an extension tube. As used herein, the term end effector means the actual working part of the surgical instrument and can include clamps, graspers, scissors, staplers, and needle holders, for example.
To perform endoscopic surgical procedures, the surgeon passes these working tools or instruments through the cannula sleeves to an internal surgical site and manipulates them from outside the abdomen. The surgeon may monitor the procedure within the internal surgical site by means of an endoscope, also referred to herein an endoscopic camera. Minimally invasive surgeries where an endoscopic camera is used are well known (e.g., arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy, urethroscopy and the like).
After each surgery, federal and state health regulations require that surgical tools be treated to prevent infection. Surgical tools that are to be reused are often cleaned, disinfected, and then sterilized after use in a prior surgery. Surgical tools may be cleaned with water, an enzymatic cleanser, and a scrub brush. Common methods of disinfecting surgical tools involves bathing them in a chemical disinfectant so that the surgical tool can be passed around within a hospital with a low level risk of infection. However, after being disinfected, a surgical tool shouldn't be used for surgery as not all bacterial has been killed. A surgical tool that is to be reused in another surgery should undergo a further sterilization process where all bacterial are killed so that the tool can be used again for surgery without transmitting bacteria from one patient to another. The sterilization process involves either a chemical sterilization using chemical sterilization techniques or a steam sterilization process using an autoclave.
Disinfection and sterilization by immersion in a chemical liquid may not be as environmentally friendly. Disposal of the used chemical is costly and may cause harm to the environment. Another drawback is that the chemicals are generally corrosive. Furthermore, chemical disinfection and sterilization may be slower than other methods. Thus, a surgical instrument may have greater lag time between surgeries.
Similarly, disinfection and sterilization using chemical gases such as ethylene oxide also have their drawbacks. Such gases are highly toxic and/or flammable. Extreme care must be used during and after the disinfection and sterilization process to ensure the safety of both the patient and medical staff. Disinfection and sterilization using gases may be complicated. A surgical instrument may have greater lag time between surgeries.
Almost all medical facilities have an autoclave and prefer to use steam sterilization of surgical instruments when they can. Commonly known as autoclave sterilization, this method of sterilization rapidly and effectively sterilizes surgical instruments without toxic chemicals and lengthy procedures. Autoclaving standards vary but two common standards require 134 degrees centigrade (C) at 2 atmospheres for 3 minutes (U.S. Standard) and 134 degrees Celsius at 2 Atmospheres for 18 minutes (European Standard). Autoclaving requires less time than other disinfection methods and does not require the use of toxic chemicals. However, some surgical instruments can't tolerate the heat and moisture from steam sterilization in an autoclave.
The steam from autoclaving may cause conventional endoscopes to fail. Pressurized steam may damage the adhesives, optics, electronics, focusing mechanisms, and opto-electronics (e.g., image capturing circuit). Moisture in the endoscope may also condense on a lens and blur images. The adhesive mount for the lens of an endoscope may be adversely affected by the heat and moisture of an autoclave. A stereoscopic lens system is especially susceptible to autoclave damage, because the relative alignment of the right and left lenses (optical paths) is important to rendering depth in the stereo image. Heat deformation of a lens mount due to thermal expansion effects may alter the relative alignment of the stereoscopic lenses.